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Title: Crystal Structure of the Zinc-Binding Transport Protein ZnuA from Escherichia coli Reveals an Unexpected Variation in Metal Coordination

Abstract

Bacterial ATP-binding cassette transport systems for high-affinity uptake of zinc and manganese use a cluster 9 solute-binding protein. Structures of four cluster 9 transport proteins have been determined previously. However, the structural determinants for discrimination between zinc and manganese remain under discussion. To further investigate the variability of metal binding sites in bacterial transporters, we have determined the structure of the zinc-bound transport protein ZnuA from Escherichia coli to 1.75 {angstrom} resolution. The overall structure of ZnuA is similar to other solute-binding transporters. A scaffolding {alpha}-helix forms the backbone for two structurally related globular domains. The metal-binding site is located at the domain interface. The bound zinc ion is coordinated by three histidine residues (His78, His161 and His225) and one glutamate residue (Glu77). The functional role of Glu77 for metal binding is unexpected, because this residue is not conserved in previously determined structures of zinc and manganese-specific transport proteins. The observed metal coordination by four protein residues differs significantly from the zinc-binding site in the ZnuA transporter from Synechocystis 6803, which binds zinc via three histidine residues. In addition, the E. coli ZnuA structure reveals the presence of a disulfide bond in the C-terminal globular domain that is not presentmore » in previously determined cluster 9 transport protein structures.« less

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930382
Report Number(s):
BNL-81104-2008-JA
Journal ID: ISSN 0022-2836; JMOBAK; TRN: US200904%%665
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Molecular Biology; Journal Volume: 368; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL STRUCTURE; DISULFIDES; ESCHERICHIA COLI; FUNCTIONALS; HISTIDINE; MANGANESE; PROTEIN STRUCTURE; PROTEINS; RESIDUES; RESOLUTION; TRANSPORT; ZINC; ZINC IONS; national synchrotron light source

Citation Formats

Li,H., and Jogl, G.. Crystal Structure of the Zinc-Binding Transport Protein ZnuA from Escherichia coli Reveals an Unexpected Variation in Metal Coordination. United States: N. p., 2007. Web. doi:10.1016/j.jmb.2007.02.107.
Li,H., & Jogl, G.. Crystal Structure of the Zinc-Binding Transport Protein ZnuA from Escherichia coli Reveals an Unexpected Variation in Metal Coordination. United States. doi:10.1016/j.jmb.2007.02.107.
Li,H., and Jogl, G.. Mon . "Crystal Structure of the Zinc-Binding Transport Protein ZnuA from Escherichia coli Reveals an Unexpected Variation in Metal Coordination". United States. doi:10.1016/j.jmb.2007.02.107.
@article{osti_930382,
title = {Crystal Structure of the Zinc-Binding Transport Protein ZnuA from Escherichia coli Reveals an Unexpected Variation in Metal Coordination},
author = {Li,H. and Jogl, G.},
abstractNote = {Bacterial ATP-binding cassette transport systems for high-affinity uptake of zinc and manganese use a cluster 9 solute-binding protein. Structures of four cluster 9 transport proteins have been determined previously. However, the structural determinants for discrimination between zinc and manganese remain under discussion. To further investigate the variability of metal binding sites in bacterial transporters, we have determined the structure of the zinc-bound transport protein ZnuA from Escherichia coli to 1.75 {angstrom} resolution. The overall structure of ZnuA is similar to other solute-binding transporters. A scaffolding {alpha}-helix forms the backbone for two structurally related globular domains. The metal-binding site is located at the domain interface. The bound zinc ion is coordinated by three histidine residues (His78, His161 and His225) and one glutamate residue (Glu77). The functional role of Glu77 for metal binding is unexpected, because this residue is not conserved in previously determined structures of zinc and manganese-specific transport proteins. The observed metal coordination by four protein residues differs significantly from the zinc-binding site in the ZnuA transporter from Synechocystis 6803, which binds zinc via three histidine residues. In addition, the E. coli ZnuA structure reveals the presence of a disulfide bond in the C-terminal globular domain that is not present in previously determined cluster 9 transport protein structures.},
doi = {10.1016/j.jmb.2007.02.107},
journal = {Journal of Molecular Biology},
number = 5,
volume = 368,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}